A shoe sole that has a reinforcing member conforming to the shape of the arch of the midsole in the arch portion, for example, a shoe sole in which a portion of the midsole not attached to the outer sole does not have ground contact when the outer sole is grounded, is known. Such a reinforcing structure increases the rigidity of the arch portion of the midsole by suppressing deformation of the midsole. Examples of such known structures are shown in FIG. 9(a), FIG. 9(b), FIG. 10(a), FIG. 10(b) and FIG. 10(c).
FIG. 9(a) is a side view of a shoe sole disclosed in Japanese Patent Laid Open No. 10-155511 (Abstract, therein) (publication date: Jun. 16, 1998). This shoe sole is provided with a supporting member 3 for supporting deformation of the arch of the foot on the top surface of a midsole 2. A space R is provided between the supporting member 3 and the midsole 2.
FIG. 9(b) is a bottom view of a shoe sole disclosed in Japanese Utility Model Registration Publication No. 3070442 (FIG. 2, therein) (registration date: May 10, 2000). This shoe sole has, a shock-absorbing member 3 composed of a sealed container attached to the bottom surface of the midsole 2. The shock-absorbing member 3 functions as a so-called shank and maintains the shape of the shoe sole.
FIG. 10(a) is a sectional view of a shoe sole disclosed in Japanese Utility Model Laid Open No. 7-44268 (Abstract, therein) (publication date: Nov. 14, 1995). In this shoe sole, a concave part C is formed at the rear foot part of the midsole 2. The concave part C is provided with a reinforcing piece 3 for preventing deformation of the rear foot part.
FIG. 10(b) is a side view of a shoe sole disclosed in Japanese Patent Laid Open No. 2003-19004 (FIG. 5, therein) (publication date: Jan. 21, 2003). In this shoe sole, an arch C is formed at the bottom of an arch portion of the midsole 2. A first reinforcing member 3 is attached to the bottom surface of the arch C and a second reinforcing member 4 is provided below the first reinforcing member 3.
FIG. 10(c) is a side view of a shoe sole disclosed in Japanese Patent Laid Open No. 2000-139508 (Abstract, therein) (publication date: May 23, 2000). In this shoe sole, end portions 3f and 3b, located forward and backward of a reinforcing member 3 on the bottom surface of a midsole 2, are wedged between the midsole 2 and an outer sole 1. This prevents the depression of the arch of the midsole 2.    The first patent document: Japanese Patent Laid Open No. 10-155511 (abstract)    The second patent document: Japanese Utility Model Registration Publication No. 3070442 (FIG. 2)    The third patent document: Japanese Utility Model Laid Open No. 7-44268 (abstract)    The fourth patent document: Japanese Patent Laid Open No. 2003-19004 (FIG. 5)    The fifth patent document: Japanese Patent Laid Open No. 2000-139508 (abstract)